1. Field of Invention
The present invention relates in general to improved trucks for railway cars. More specifically, but without restriction to the particular use which is shown and described, this invention relates to truck side frames that have a crowned pedestal roof.
2. Description of the Related Art
It is known that railcar trucks are the wheeled structures that support the weight of the railcar body and ride on the railroad track. As conventional, two trucks are used beneath and at each end of the railcar body. A common type of railcar truck used in freight service is the three-piece truck which comprises two parallel side frames and a truck bolster that transverses the side frames. Typically, the bolster, at each end, extends into bolster openings defined by each side frame and is supported by the side frames. The side frames and truck bolster are supported on at least two longitudinally spaced wheelsets. Each wheelset includes transversely spaced wheels that are joined by a transversely extending axle having axle ends mounted in respective bearing adapters.
The transversely spaced side frames are usually cast and comprise a bolster opening, an elongated lower tension member, and an elongated top compression member which defines longitudinally spaced, downwardly opening pedestal jaws on each end. The jaws are adapted to receive the bearing adapters which rotatably receive the journal portions of the axles. Thus, the wheel sets and side frames are mounted together by the bearing adapters.
The pedestal jaw further defines a pedestal jaw roof and a downwardly extending bracket. The pedestal jaw roof typically defines a cavity to accommodate it a crown shaped block of hardened steel that is inserted in the cavity with the crowned surface extending out from the pedestal roof. Two spacers or shims are located between the sides of the crowned block and the walls formed by the cavity. These spacers eliminate the gap between the crowned block side walls and the pedestal jaw cavity to allow the block member to fit snug within the cavity. Two retainers are welded in position to hold the block member in the cavity. Advantageously, in service, the crowned block member permits the side frame to swing or sway relative to the axle about the longitudinal axis of the side frame. Moreover, this crowned block member reduces wear in the pedestal roof. The crowned block, after it is worn, can be replaced by removing the retainers and rewelding a new crowned block member.
However, numerous components are used to form the crowned pedestal roof to permit swinging of the side arm: the block member, the two spacers, and the two retainers. In addition, removing the welded rocker seat requires significant maintenance, and replacing the crowned block and/or retainers can be costly.